Trying to understand 3-way switch and smart lighting

[The Ghost]

As to dangerous, unknown, not enough info/pics. It just worried me for a moment when you mentioned neutral/earth somewhat nonchalantly. But it sounds like it is not a neutral anyway.

 

[MJPD29]

I don't think they had the house rewired 5 years ago, more like 15 at least of theres red cables still inolved

 

[NotALeccy]

Not only am I dumb. I'm really really dumb. Having actually looked a bit more carefully, I can see that I'm energizing the earth The green and yellow is earthing on the metal frame of the holder. I can't believe I've made such a dangerous mistake. Thank you for highlighting this to me.

Here are the photos anyway, the question is, is it safe for me to reinstall the old switch and what does the blue wire do? Any help at this point would be absolutely wonderful.

Is it worth me disconnecting the earth to see if it works? On a purely academic level?

 

[westward10]

The reason it functions is because you have connected earth to the neutral terminal and I am guessing unlike you other switch this one needs a neutral to function which the earth will do however, that is not the way to go about it and you need to reinstate the original switch. I doubt the unused blue is a neutral, put the original one back but if in doubt get an electrician in to check it.

 

[Gavin John Hyde]

At least the OP seems to accept his limitations and will stop before doing damage which is a rarity as the forum normally gets the visit from DIY dave who is apparently going to use his mate the electrician but is currently on a unicorn riding holiday in never never land.

 

[westward10]

Ditch the not so smart switch and reconnect the original as your bottom picture shows.

 

[NotALeccy]

Oh for sure, it's coming out. I am happy to admit defeat on this one. I definitely need to get a pro in when doing this stuff in the future. I will get a qualified electrician in, probably after Xmas now to install it, if I decide to install it at all. It might not be worth the effort and nothing is more important than safety when it comes to your house, especially not for a bit of convenience!!!

Just while we're on the subject, how much would/should a good electrician charge to install a neutral cable? Is it a rip-the-wall out job? If so, I think I'll give it a swerve

 

[shaun1]

It may be possible to re wire the circuit to provide neutral down the existing cable but that would have to be investigated.

Also, I think you are confusing Neutral,l and Earth of a 230v A.C. system with 0v/ground in electronics. In an A.C. system, earth is connected to the Neutral at the supply end and to the general mass off earth, but from that point on it is only used as a safety system to make sure that all exposed metal work remains at 0v to earth. The Neutral cable provides a return path for all connected loads. Lighting circuits are often wired with a live and neutral in the light fitting and then a pefmenant live wire is run from the fitting to switch with a switched live running back to control the light.

As mentioned it is possible to get smart switches that don't require a neutral (these work by sitting in series with the load (bulb) and passing a small current through it even when off.

There are also smart dimmers that can be wired in at the light fitting, using the existing switch as a control input.

But as already stated, it would be best for you to find an electrician who is experienced in wiring these smart switches. If you find the right solution it may only involve a couple of hours of labour to get a few circuits wired up to smart switches. All tested and certificates issued.

 

[The Ghost]

What worries me, having established the earth is energised (possibly) is why did the RCD not trip. I applaud @NotALeccy your honesty in checking and listening and "owning" up to what is a very understandable mistake in the circumstances. Can you put up a picture of the box which controls this circuit so we could see if you do have an RCD.

 

[shaun1]

The N connector in the switch is only for the switch electronics, which probably only draws a couple of w so may not be enough current to trip the RCD